Maybe this is what Patrick's referring to, from Kirkham's website?:
Options and Accessories Info
Not necessary on an ERA (as I said earlier, coremat is embedded in the fender wells). Still, I plan to spray undercoating in my wheel wells - to deaden the sound of rocks pinging around a bit but also because I like the look of black wheel wells as opposed to aluminum. Yet another "to each his own" thing, I suppose.
Regards,
Kevin